Published: Tue, July 17, 2018
Research | By Jody Lindsey

Astronomers just discovered 12 new moons around Jupiter


Scott Sheppard: "It's been about a decade since the last moons around Jupiter were discovered".

But Sheppard suspects these moons could be holdouts, the "last remnants" of early solar system objects.

One of a dozen new moons discovered around Jupiter is circling the planet on a suicide orbit that will inevitably lead to its violent destruction, astronomers say. University of Hawaii's Dave Tholen and Northern Arizona University's Chad Trujillo are also part of the planet search team.

"Jupiter just happened to be in the sky near the search fields where we were looking for extremely distant Solar System objects, so we were serendipitously able to look for new moons around Jupiter while at the same time looking for planets at the fringes of our Solar System", said Sheppard. We're using the most advanced digital cameras in the world ... This proved to be quite helpful, as the unknown moons around Jupiter are small and dim.

"This is really cool and really exciting", astronomer Jonti Horner of the University of Southern Queensland, who was not involved in the research, told ScienceAlert. As for the number of satellites that orbit Jupiter, Williams said he dreads "to think how many objects are in the hundred-meter range".

Gareth Williams, an astronomer at the Harvard-Smithsonian Center for Astrophysics and director at the International Astronomical Union's Minor Planet Center, predicted that "there aren't any bigger objects undiscovered out there" around Jupiter. Most of these prograde moons take less than a year to travel around the planet.

Two of the newly discovered moons orbit much closer to Jupiter and have a prograde orbit, meaning that they orbit in the same direction as the planet. "This is an unstable situation", continued Sheppard. They are thought to be the remnants of larger parent bodies that were broken apart in collisions with asteroids, comets and other moons. "What these other objects were has been a mystery". These two newly discovered moons take a little less than a year to travel around Jupiter.

Because it's orbiting in the opposite direction of the nine "new" retrograde moons, and across their paths, there is a high risk that it will hit one of them, according to the statement.

Two of them are pretty straightforward. These are part of a group of prograde moons that orbit closer to Jupiter than the retrograde moons do.

Washington, DC-Twelve new moons orbiting Jupiter have been found-11 "normal" outer moons, and one that they're calling an "oddball".

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"Our other discovery is a real oddball and has an orbit like no other known Jovian moon", Sheppard explained.

Tentatively named Valetudo, after the Roman goddess of health and cleanliness, and great-granddaughter of Jupiter, the moon is more distant and more inclined than the group of inner prograde moons.

It takes around 18 months to orbit Jupiter, and its orbit passes that of the retrograde moons, which makes collisions pretty likely. It has a prograde orbit at a distance where the rest of Jupiter's moons have retrograde orbits.

The team believes Valetudo might be a fragment of a larger moon, broken off in a collision with a larger retrograde moon, resulting in something like the retrograde groupings observed.

It's possible the various orbital moon groupings we see today were formed in the distant past through this exact mechanism.

Most moons, including Earth's, have prograde orbits.

Finding a moon that tiny, he noted, means it must have formed after all the gas and dust had cleared.

Our solar system is already teaming with almost 200 moons, and we just got 12 more to add to the list.

Sheppard and his team already proposed a name for the rebel moon. The astronomers are now running computer simulations to determine how the ancient moons fragmented.

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